The use of catheters in the removal of or the injection of fluids into an animal body are well known. Typically, such catheters comprise a tubular element with a central bore or lumen having a distal opening and/or longitudinal openings to the bore of the catheter. The catheter body may be rigid, semi-rigid or flexible depending upon the specific use for which it is designed.
A flexible catheter having a specific shape for use in a coronary arteriography is disclosed in U.S. Pat. No. 4,117,836. U.S. Pat. No. 4,033,331 discloses a cardiac catheter which is flexible in which the distal end has a memory or set curvature. The flexibility is controlled by a stiffening wire inserted into a lumen separate from and parallel to the main fluid lumen of the catheter.
U.S. Pat. Nos. 3,920,023 and 3,860,006 disclose flexible suprapubic catheters which include shaped ends to minimize pull-out after installation. U.S. Pat. Nos. 3,419,010 and 4,586,338 disclose flexible catheters which have distal ends with a memory for a preformed shape.
Typically, in intra-amniotic techniques such as percutaneous umbilical blood sampling (PUBS) straight, rigid needles are employed. Curent technological advances have made direct access to fetal blood during the second and third trimesters of pregnancy feasible. The ability of sample fetal blood allows more accurate prenatal fetal diagnosis and evaluation and therapy.
The existing PUBS techniques involve the insertion of a straight needle into the umbilical vessels in the region of the junction of the umbilical cord and placenta under direct ultrasonography visualization. While this procedure has an acceptable complication rate and is generally accepted, there are procedural and technical limitations. For example, with obese patients manipulation of the inserted needle in the intra-amniotic space is limited.
In some cases, fetal position or the fixation point of the umbilical cord may prevent access to the junction. In cases of oligohydramnios, the decreased amount of amniotic fluid may limit the visualization of the umbilical cord/placental junction by ultrasonographic techniques. Also, the angle of the abdominal skin level for the needle insertion may limit the manipulation of a straight needle for optimum orientation. Because of movement of the free floating umbilical cord, sampling at other than the umbilical cord/placental junction has been unknown.